This application claims the benefit of Japanese Patent Application 2000-278471 filed Sep. 13, 2000.
The present invention relates to a cable drag chain for supporting and guiding such flexible members as electric cables and hydraulic or pneumatic hoses between a fixed portion and a movable portion of a machine tool, an earth-moving machine, a conveyor and so on.
Cable drag chains have been proposed to support and guide flexible members, such as electric cables and hydraulic or pneumatic hoses, while protecting the flexible members against damage or entanglement which may occur due to undue twisting or stretching of the flexible members during movement of the movable part of a machine tool, earth-moving machine or conveyor to which the flexible members are connected.
One example of such conventional cable drag chains is disclosed in Japanese Patent Publication No. SHO-62-15008, entitled xe2x80x9cEnergy Conduit Supportxe2x80x9d. The disclosed energy conduit support includes inner tubular members made from synthetic resin and outer tubular members made of metal and arranged alternately with the inner tubular members in the longitudinal direction of the energy conduit support. Each of the inner tubular members has two sector-like grooves formed at the outer periphery on each of two opposite side of the inner tubular member. Each of the outer tubular members is composed of a pair of upper and outer tubular member halves connected together by pins so that the pin-connected tubular member halves surround opposed end portions of two adjacent inner tubular members. The joint between the inner and outer tubular members in the longitudinal direction of the energy conduit support is formed by way of fitting engagement between the sector-like grooves of the inner tubular member and stopper projections formed on the respective inner peripheries of the outer tubular member halves.
In the energy conduit support shown in the Japanese publication specified above, since the inner tubular members are not connected together by themselves, a framework of the energy conduit support is constituted by the outer tubular member halves pined together to form an outer tubular member. Due to this construction, the conventional energy conduit support as a whole has a relatively low torsional rigidity. In addition, since the bending angle of the energy conduit support is limited by abutting engagement between the grooves of the inner tubular members and the stopper projections of the outer tubular members, the energy conduit support is likely to be damaged when subjected to a relatively large force.
When pins are removed, the outer tubular member halves and the adjacent inner tubular members are disconnected from one another, thus forming a break or interruption in the energy conduit support. Reassembling of the inner and outer tubular members to mend the break is uneasy to achieve. In addition, once the outer tubular member halves and the inner tubular members are assembled together, disassembling work of these components is tedious and time-consuming. When the disassembled components are to be assembled again, the pins must be replaced with new ones. This replacement increases the cost of the energy conduit support and makes the energy conduit support unsuitable for an application in which a frequent maintenance and inspection is a major requirement.
Furthermore, the inner tubular members made from synthetic resin are susceptible to abrasive wear and produce plastic powder due to friction contact with the outer tubular member halves made of metal during use of the energy conduit support. Use of the metallic material increases the overall weight of the energy conduit support and produces a great noise when the metallic outer tubular members abut on the adjacent plastic inner tubular member or beat the floor surface during use of the energy conduit support.
With the foregoing problems in view, it is an object of the present invention to provide a cable drag chain which has relatively large bending and torsional rigidities and hence can hold flexible members safely against undue bending or twisting, is light in weight, can be manufactured at a relatively low cost, produces little abrasive powder, is easy to assemble and maintain and produces little noise during use.
According to the present invention, there is provided a cable drag chain comprising a plurality of ring-like inner links pivotally connected together end to end. Each of the inner links has a pair of connecting pins formed at one end thereof, a pair of pin holes formed at the opposite end thereof for receiving the connecting pins of an adjacent one of the inner links to thereby connect two adjacent ones of the inner links, and end faces formed at the front and rear ends of the inner link and serving as stopper surfaces engagable with the stopper surfaces of the adjacent inner links to limit the angle of pivotal movement between the adjacent inner links. The cable drag chain further includes a plurality of outer links, each outer link being detachably mounted to a joint portion between two adjacent one of the inner links and surrounding the joint portion so as to close a space formed between the two adjacent inner links.
In one preferred form of the present invention, the inner link has two circumferential grooves spaced in an axial direction of the inner link, and the outer link has a pair of annular end flanges formed at opposite ends thereof. The end flanges being received in adjacent two circumferential grooves of each pair of adjacent inner links. The hollow interior space formed in the cable drag chain is fully closed so that dust produced inside the cable drag chain is held within the closed hollow interior space without leakage.
It is preferable that when the stopper surfaces of two adjacent inner links are in contact with each other, the outside distance between the end flanges of the outer link is larger than the distance between opposed sidewalls of the adjacent two circumferential grooves with which the end flanges are engaged. By virtue of the dimensional difference, the end flanges engage the sidewalls of the circumferential grooves in advance to the abutment between the stopper surfaces of two adjacent inner links, thereby lessening a collision sound of the cable drag chain. To enhance the noise reducing effect, a synthetic resin forming the outer link is more flexible than a synthetic resin forming the inner link.
It is preferable that the inner link is molded of a synthetic resin, and the outer link is molded of a synthetic resin.
In one preferred form of the present invention, the outer link is composed of a pair of outer link members of an identical shape and configuration detachably connected at opposite ends, one end of each outer link member has a connecting pin, and the other end of each link member has a pin hole for receiving therein the connecting pin.
In another preferred form of the present invention, the outer link is comprised of a hinged one-piece outer link having a hinge portion at one side thereof and a pin and pin-hole connection at the other side of thereof.